Buggy code:
public abstract class ToStringStyle implements Serializable { public static final ToStringStyle DEFAULT_STYLE = new ToStringStyle . DefaultToStringStyle ( ) ; public static final ToStringStyle MULTI_LINE_STYLE = new ToStringStyle . MultiLineToStringStyle ( ) ; public static final ToStringStyle NO_FIELD_NAMES_STYLE = new ToStringStyle . NoFieldNameToStringStyle ( ) ; public static final ToStringStyle SHORT_PREFIX_STYLE = new ToStringStyle . ShortPrefixToStringStyle ( ) ; public static final ToStringStyle SIMPLE_STYLE = new ToStringStyle . SimpleToStringStyle ( ) ; private static final ThreadLocal registry = new ThreadLocal ( ) { @ Override protected Object initialValue ( ) { } } ; static Set getRegistry ( ) { } static boolean isRegistered ( Object value ) { } static void register ( Object value ) { } static void unregister ( Object value ) { } private boolean useFieldNames = true ; private boolean useClassName = true ; private boolean useShortClassName = false ; private boolean useIdentityHashCode = true ; private String contentStart = "[" ; private String contentEnd = "]" ; private String fieldNameValueSeparator = "=" ; private boolean fieldSeparatorAtStart = false ; private boolean fieldSeparatorAtEnd = false ; private String fieldSeparator = "," ; private String arrayStart = "{" ; private String arraySeparator = "," ; private boolean arrayContentDetail = true ; private String arrayEnd = "}" ; private boolean defaultFullDetail = true ; private String nullText = "<null>" ; private String sizeStartText = "<size=" ; private String sizeEndText = ">" ; private String summaryObjectStartText = "<" ; private String summaryObjectEndText = ">" ; protected ToStringStyle ( ) { } public void appendSuper ( StringBuffer buffer , String superToString ) { } public void appendToString ( StringBuffer buffer , String toString ) { } public void appendStart ( StringBuffer buffer , Object object ) { } public void appendEnd ( StringBuffer buffer , Object object ) { } protected void removeLastFieldSeparator ( StringBuffer buffer ) { } public void append ( StringBuffer buffer , String fieldName , Object value , Boolean fullDetail ) { } protected void appendInternal ( StringBuffer buffer , String fieldName , Object value , boolean detail ) { } protected void appendCyclicObject ( StringBuffer buffer , String fieldName , Object value ) { <START_BUG> ObjectUtils . appendIdentityToString ( buffer , value ) ; <END_BUG> } protected void appendDetail ( StringBuffer buffer , String fieldName , Object value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , Collection coll ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , Map map ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , Object value ) { } public void append ( StringBuffer buffer , String fieldName , long value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , long value ) { } public void append ( StringBuffer buffer , String fieldName , int value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , int value ) { } public void append ( StringBuffer buffer , String fieldName , short value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , short value ) { } public void append ( StringBuffer buffer , String fieldName , byte value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , byte value ) { } public void append ( StringBuffer buffer , String fieldName , char value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , char value ) { } public void append ( StringBuffer buffer , String fieldName , double value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , double value ) { } public void append ( StringBuffer buffer , String fieldName , float value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , float value ) { } public void append ( StringBuffer buffer , String fieldName , boolean value ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , boolean value ) { } public void append ( StringBuffer buffer , String fieldName , Object [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , Object [ ] array ) { } protected void reflectionAppendArrayDetail ( StringBuffer buffer , String fieldName , Object array ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , Object [ ] array ) { } public void append ( StringBuffer buffer , String fieldName , long [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , long [ ] array ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , long [ ] array ) { } public void append ( StringBuffer buffer , String fieldName , int [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , int [ ] array ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , int [ ] array ) { } public void append ( StringBuffer buffer , String fieldName , short [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , short [ ] array ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , short [ ] array ) { } public void append ( StringBuffer buffer , String fieldName , byte [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , byte [ ] array ) { } protected void appendSummary ( StringBuffer buffer , String fieldName , byte [ ] array ) { } public void append ( StringBuffer buffer , String fieldName , char [ ] array , Boolean fullDetail ) { } protected void appendDetail ( StringBuffer buffer , String fieldName , char [ ] array ) { }

Fix:
ObjectUtils . identityToString ( buffer , value ) ;